After losing a silkie and being forced to care for a badly injured one, I installed a baby monitor inside the coop so I can hear anything that may be happening.
This is great! I am sitting here listening to crickets outside the coop.....this thing is sensitive enough to clearly pick them up. It has a range of 400 feet, but I saw some with a longer range.
I paid 20 bucks for it at Target.
I got the model that also has little lights that flash wih the intensity of noise. That way if I don't want to have it turned up I can just watch for the lights. It also has a built in nightlight on the transmitter part (inside the coop) that lights up a corner with soft light.

I didn't get the video version, because I wasn't sure how much light had to be present to be able to see at night.
I'm guessing not much if they are designed for a baby's bedroom at night.....
I will keep this turned on day and night, as it was during the day when my roo was murdered and my hen was hurt.
I'm sure there was quite a ruckus going on out there during this event.
I could have run outside or sent my dogs....dang.

I've always had one in the coop. I can even hear what's going on, to a degree, in the other coops. I can hear dogs nextdoor barking and raising cain at night and I could certainly hear voices of someone near my coops talking or the barrel bolt unlocking if someone was trying to steal my birds.

I've got a baby monitor sitting around somewhere...I've found the part that goes in the house, but I need to dig and see if I can find the part that goes in the baby's room. I heard someone else had done this and have been planning it ever since. I think it's a great idea. I'd love to get a video monitor, but that's not an option at the moment. Hopefully before too long.